The present invention relates to a side door structure for a vehicle, which structure consists of front and rear doors and, more particularly, to a side door structure for a vehicle, which can improve safety in the case of a rear or side collision.
As a conventional side door structure for a vehicle, which can improve safety against a collision from a side of a vehicle (i.e., a side collision), the following technique is known. More specifically, as described in, e.g., Japanese Patent Publication No. 6323004, an impact bar (door guard bar) extending in the back-and-forth direction of a vehicle body is arranged in each of front and rear doors constituting side doors of a sedan type vehicle, and a collision energy acting on each side door is absorbed by the impact bar.
In the conventional side door structure for a vehicle, which comprises the impact bars, since the rigidity of each of the front and rear doors is increased, a deformation of the side doors can be minimized in a side collision of the vehicle. However, when a collision from the rear side of the vehicle (i.e., a rear collision) occurs, the rear doors are moved forward since they are pushed by rear fenders deformed by the rear collision, and opposing portions between the front and rear doors may crush each other. In this manner, when the front edge portion of the rear door is deformed to cover the rear edge portion of the front door, a so-called dead lock phenomenon in which the front doors are difficult to be opened/closed, occurs.
The following countermeasures in terms of the layout of a vehicle structure may be taken. For example, the front edge of the rear door and the rear edge of the front door may be sufficiently separated in the back-and-forth direction of a vehicle body, or the front edge of the rear door may be assembled to be originally displaced inwardly from the rear edge of the front door. However, such countermeasures cause a poor outer appearance of the vehicle body, and may decrease the purchasing will of consumers. In addition, these countermeasures narrow the space of a rear passenger room, thus posing a problem of comfort for passengers seating on the rear seats Thus, these countermeasures cannot be taken.
For this reason, in order to prevent the dead lock phenomenon, a guide mechanism for guiding the front edge portion of the rear door inwardly in the vehicle body upon a rear collision, so that the front edge of the rear door does not overlap the rear edge of the front door must be arranged. However, when the guide mechanism is adopted, the side door structure is complicated, and the weight of the vehicle is undesirably increased due to the weight of the guide mechanism.
In the above-mentioned reference, each impact bar is arranged at the same level as a bumper of a colliding vehicle. As a result, the position of the impact bar corresponds to the waist position of a seating passenger. In some cases, the shock of the collision cannot be absorbed by the impact bar depending on collision levels. In this case, the impact bar may enter the passenger room, and may hit the waist of a seating passenger.